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What to do with XOSC pins when using internal oscillator for hibernation module?

Robert Stoddard64964
Prodigy 270 points

I have looked at the documentation (datasheet and whatnot) and it suggests that the hibernation module can be used with a rather inaccurate internal oscillator.  It goes into detail about how to set that up in software, however, there's no mention of what I should do with the XOSC pins should I want to go this route.  My application cares not a whit about the accuracy of the clock at any time, so I'm very interested in saving the components and not using an external xtal.  What should I do with these pins?  Leave them floating?  Tie them to ground?  Hook up capacitors?   Attach them to an LF yagi antenna that's pointed towards Forest Lane?  (sorry, sense of humor is getting the best of me)

Thank you


Rob

  • 0
    TI__Guru**** 244400 points

    Hello Robert

    Please check the System Design Guidelines for TM4C129x. It does tell what to do with unused pins.

    http://www.ti.com/lit/pdf/spma056

    Regards

    Amit

  • 0 in reply to Amit Ashara
    TI__Prodigy 270 points

    I am familiar with this document.  It is pretty clear in stating that unused pins could/should be left floating, however, I was unsure whether that applied to XOSC pins as well.  On that note, there is plenty of information regarding what to do if you have a single-ended oscillator or a crystal.   I suppose then, I should leave both XOSC pins floating.  But typically the information is applied towards GPIOs or signal pins, which XOSC is neither.   So I figure it'd be best to check.   I'd sure like to save on the components and simply not have the xtal and capacitors for a clock I do not need, but I want to make sure that I don't end up with a boat-anchor device because I did the wrong thing wiht these lines.

  • 0 in reply to Robert Stoddard64964
    TI__Guru**** 244400 points

    Hello Robert,

    When not using the Oscillator Pins then OSC0 (for main oscillator) and XOSC0 (for 32KHz Hibernate Oscillator) must be connected to GND This prevents stray noise from entering the clock detection circuit.

    Regards,

    Amit